Django 通过 ORM 实现表的CRUD
单表的创建
- 修改 setting.py 文件
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': '数据库名称',
'USER': '用户名',
'PASSWORD': '密码',
'HOST': '127.0.0.1',
'PORT': '3306',
}
}
- 修改应用下面对应的models.py 文件
class Book(models.Model):
nid = models.AutoField(primary_key=True) # 表ID 自增主键
title = models.CharField(max_length=32) # 字符串，最大长度为32
price = models.DecimalField(max_digits=8, decimal_places=2) # 小数，最多8位，小数点最多2位
publish = models.CharField(max_length=32)
pub_date = models.DateTimeField()
- 修改在与 setting.py 同级的目录下的 _ init_.py 文件
import pymysql
pymysql.install_as_MySQLdb()
- 执行以下脚本在应用下创建 migrations 包以及相应的类
python manage.py makemigrations
- 执行以下脚本会在数据库中创建 INSTALLED_APPS 中所有对应的数据表
python manage.py migrate
Django 数据的插入（PS：要先完成表的生成）
from django.contrib import admin
from django.urls import path
from vedio import views
urlpatterns = [
path('admin/', admin.site.urls),
path('add/', views.add),
]
from django.shortcuts import render,HttpResponse,redirect
from vedio.models import Book
def add(request):
# 方法一
"""
book = Book(title="Django", price=123, pub_date="2019-10-06", publish="人民出版社")
book.save()
"""
# 方法二
Book.objects.create(title="Think PHP", price=123, pub_date="2019-10-06", publish="人民出版社")
# 方法三
"""
Book.objects.create(**request.POST.dict())
PS：request.POST 要删除 {{ csrf-token }} 引进了的变量
"""
return HttpResponse("OK")
Django 数据的查询，删除，修改
from django.shortcuts import render,HttpResponse,redirect
from vedio.models import Book
def books(request):
# books = Book.objects.all() # 返回所有记录
books = Book.objects.filter(title="Think PHP") # 查询标题等于 Think PHP的所有记录
# Book.objects.filter(title="Think PHP").delete() # 删除标题为 Think PHP的所有条记录
# Book.objects.filter(nid=1).update(price=120) # 更新 nid=1 这条数据的price
return render(request, "books.html", locals())
from django.contrib import admin
from django.urls import path
from vedio import views
urlpatterns = [
path('admin/', admin.site.urls),
path('books/', views.books),
]
Django 查询深入
from django.shortcuts import render,HttpResponse,redirect
from vedio.models import Book
def books(request):
# all()
# books = Book.objects.all() # 返回所有记录
# filter()
# books = Book.objects.filter(title="Think PHP") # 查询标题等于 Think PHP的所有记录
# books = Book.objects.filter(title="Think PHP", nid=2) # 查询标题等于 Think PHP 并且 nid = 2 的所有记录
# get()
# books = Book.objects.get(title="Think PHP") # 查询标题等于 Think PHP 的一条记录，大于1条或1条都没有将报错
# first() last()
# books = Book.objects.all().first() # 返回 queryset 的第一个 model 对象
# books = Book.objects.all().last() # 返回 queryset 的最后一个 model 对象
# exclude()
# books = Book.objects.exclude(title="Django") # 查询 title 不等于 Django 的 querySet
# order_by()
# books = Book.objects.all().order_by('price') # 根据price 升序
# books = Book.objects.all().order_by('-price') # 根据price 降序
# count()
# books_num = Book.objects.all().count() # 返回书籍的个数
# reverse()
# books = Book.objects.all().reverse() # 逆序
# exits()
# is_exits = Book.objects.all().exists() # 判断数据表是否有数据
# values()
# ret = Book.objects.all().values('title', 'price') # 取 title price 的数据，返回一个列表，列表里面的数据是字典
# values_list()
# ret = Book.objects.all().values_list('title', 'price') # 取 title price 的数据，返回一个列表，列表里面的数据是元组
# distinct()
# books = Book.objects.all().values("title").distinct() # 对 title 中的数据进行去重
# __gt __lt __gte __lte
# books = Book.objects.filter(price__gt=200) # 查询 price 大于200 的数据
# books = Book.objects.filter(price__gte=200) # 查询 price 大于等于200 的数据
# books = Book.objects.filter(price__lt=200) # 查询 price 小于200 的数据
# books = Book.objects.filter(price__lte=200) # 查询 price 小于等于200 的数据
# __startswith __istartswith __contains __icontains
# books = Book.objects.filter(title__startswith="Think") # 查询 title 以 Think 开头的数据
# books = Book.objects.filter(title__istartswith="think") # 查询 title 以 Think 开头的数据，不区分大小写
# books = Book.objects.filter(title__contains="Think") # 查询 包含 Think 的数据
return render(request, "books.html", locals())
Django 一对多表的创建
from django.db import models
class Book(models.Model):
nid = models.AutoField(primary_key=True) # 表ID 自增主键
title = models.CharField(max_length=32) # 字符串，最大长度为32
price = models.DecimalField(max_digits=8, decimal_places=2) # 小数，最多8位，小数点最多2位
pub_date = models.DateTimeField()
publish = models.ForeignKey(to="Publish", on_delete=models.CASCADE) # on_delete=models.CASCADE 指定级联删除
class Publish(models.Model):
nid = models.AutoField(primary_key=True)
name = models.CharField(max_length=32)
email = models.CharField(max_length=32, null=True) # null=True表示该字段可以为空
Django 多对多表的创建
from django.db import models
class Book(models.Model):
nid = models.AutoField(primary_key=True) # 表ID 自增主键
title = models.CharField(max_length=32) # 字符串，最大长度为32
price = models.DecimalField(max_digits=8, decimal_places=2) # 小数，最多8位，小数点最多2位
pub_date = models.DateTimeField()
publish = models.ForeignKey(to="Publish", on_delete=models.CASCADE) # on_delete=models.CASCADE 指定级联删除
authors = models.ManyToManyField(to="Author") # 指定多对多
class Author(models.Model):
nid = models.AutoField(primary_key=True)
name = models.CharField(max_length=32)
age = models.IntegerField()
email = models.CharField(max_length=32)
Django 一对一表的创建
from django.db import models
class Author(models.Model):
nid = models.AutoField(primary_key=True)
name = models.CharField(max_length=32)
age = models.IntegerField()
email = models.CharField(max_length=32)
ad = models.OneToOneField(to="AuthorDetail", on_delete=models.CASCADE)
class AuthorDetail(models.Model):
addr = models.CharField(max_length=32)
tel = models.IntegerField()
Django 一对多数据的插入
Book.objects.create(title="Python")
Django 多对多数据的插入
book = Book.objects.create(title="Django")
# 方法一
zp = Author.objects.filter(name="zp").first()
mcx = Author.objects.filter(name="mcx").first()
book.authors.add(zp, mcx)
# 方法二
book.authors.add(1, 2)
# 方法三
book.authors.add(*[1, 2])
Django 多对多数据的解除绑定
book = Book.objects.filter(title="Django").first()
mcx = Author.objects.filter(name="mcx").first()
book.authors.remove(mcx) # 删除 与 book 关联的 mcx
book.authors.clear() # 删除 与 book 关联的所有作者
Django 多对多数据的解除再绑定
book = Book.objects.filter(title="Django").first()
# 方法一
book.authors.clear()
book.authors.add(1)
# 方法二
book.authors.set(1)